It wasn't too long ago, just a few hundred years really, that most breeds of dog would have lived in the wilderness, roamed wild, had no interest in humans, and enjoyed nothing more than chasing down and ripping apart any prey to be found. No matter what methods we use to train, those instincts will always and forever be a part of the mental make-up of your dog. Many breeds have adapted this behavior to physical play and rough housing with other dogs, playing with owners, and hunting chew toys. This type of activity is a much needed outlet for any dog, especially a Jack Russell in order to release pent up energy and stress. These dogs have adapted those hunter/killer instincts into something to do for fun without anyone getting hurt (most of the time). This "fun" is necessary for many breeds, especially the Jack Russell, in order to cope with the change in lifestyle and living conditions that their ancestors enjoyed. When you bring a Jack Russell into a home that demands no physical interaction, excitement, rough housing and above all physical communication, you are taking away the one tool that they have in order to deal with their unnatural surroundings; the lifestyle of being an obedient pet as opposed to a wild carnivorous beast.

This is why physical outdoor activity is so important for a Jack Russell. The reason that he has hunted your home and ripped apart your leather jacket is because you aren't giving him an outlet to expend his natural aggression. To him even the destruction of a sandal is a small victory and a successful hunt. When the dog is punished and scolded for this behavior they don't understand what it is that they have done to incur your wrath. Until you had become irate with them, they were proud of their accomplishment and believed they had done a good thing.